I recently acquired a Graflex 16 Projector, Model #920. Some previous owner messed with the circuitry. Some wires are disconnected. I was told that it was O.K. mechanically, but the sound might not work. Is there a way that I can find a copy of the electrical schematic for this unit? I am a little concerned about plugging it in and turning it on. There is a large mystery switch in the middle of the rear section down near the base. Any ideas? Thank you very much for reading my post. Larry_________________Larry of New Hampshire